Rewrite file naming, redirection support etc
Rewrite file naming, redirection support etc

File naming code rewritten. Hopefully wont trash your file system anymore
- If available, uses content-disposition header as a filename source
- Strict charset rules for filenames (maybe a little too strict?)
- Special rules for spaces and dots
- No file will be written with invalid file extensions

HTTP redirection support (close #14)
- Supports redirection with most relevant status codes. 

Dropbox embed support (mentioned in issue #13 + more info)
- Works with images linked in format https://www.dropbox.com/s/<random>/<filename>?dl=1

Embed quicksave button:
- Will now again bind to loading images, resolving #12
- Progress bar. Implemented with bleeding-edge unicode block elements.
kosshishub/Quicksave-BD-plugin